Gene Therapy in India- Current Status

Introduction

Gene therapy is an attempt to treat diseases by replacing defective gene with healthy genes or repairing the defective genes in order to improve the function of genes. World was first introduced to gene therapy in 1995 almost two decades ago when Blaese et al published his initial trial results of T lymphocyte directed gene therapy in Adenosine Deaminase (ADA) deficiency associated Severe Combined Immunodeficiency (SCID) (1).

Hindrances to gene therapy started following three deaths which occurred just after clinical initiation of gene therapy. One was due to multiple organ failure as a consequence of severe immune response to the viral vector and other two children died of leukemia (2, 3). These deaths raised issues of ethical concern following gene therapy and lead to complete halt of the trials all over the world. After the initial set back, interest later renewed almost a decade later in the year 2008, when gene therapy restored vision in three young children suffering from Leber's congenital amaurosis (4). After these successful results of gene therapy, United States of America and Europe became the pioneers in gene therapy-related studies and clinical trials. In Asian continent, China and Japan have emerged as the forerunners in the stem cell research, with China launching Gendicine, an injectable gene therapy product (a replication- incompetent recombinant human p53 wild type protein particles combined with adenovirus serotype 5) approved by the China Food and Drug Administration (CFDA) in 2003 for head and neck cancer. Japan has introduced Retronectin reagent, which is a recombinant human Fibronectin Fragment and on injection, enhances retroviral (as well as lentivirus, a form of retrovirus)-mediated gene transfection and transduction by helping the co-localization of target cell and virions. The reagent can enhance retroviral-mediated gene transfer to target cells that express integrin receptors VLA-4 and/or VLA-5, thus making the gene delivery more specific as the gene will not be delivered to body cells which lack VLA-4 and/or VLA-5 integrin receptors.

Types of Gene Therapy

It becomes important to understand some of the terminologies and the types that are often used in relation to gene therapy. Alternative terms like genetic engineering, Deoxyribonucleic Acid (DNA)-based therapy and molecular therapy are often used by layman and biologists. Gene therapy is one of the tool of genetic engineering used with purpose to alleviate suffering from hereditary diseases. However, genetic engineering in wider term not only aims to alter genes to correct genetic defects but may also be involved in modifying the genes to enhance the capabilities of the organism beyond what is normal. The latter is a dangerous proposition of genetic engineering.

A. Gene therapy can be classified into somatic cell and germ cell types, depending upon the type of cells that are modified by the therapeutic genes (6, 7). All the gene therapies till date are directed towards somatic cells only.

Clinical Implications

Central Nervous System (CNS) Disorders

Unlike cardiac, in neurological disorders gene therapy has shown promising results to treat Parkinsonism (12) and Alzheimer's disease (13). There have been several trials on gene therapy in Parkinsonism which are still in phase 1 and phase 2 but are showing gene therapy to be safe, tolerable and potential candidate for invivo studies (12). Various approaches used are, transmitting the gene for glutamic acid decarboxylase into the subthalamic nucleus (12) or delivery of the gene for neurturin in putamen cell bodies (14). Similarly in Alzheimer's disease gene therapy is being attempted to deliver Nerve Growth Factor gene into the human CNS (13).

Intrauterine Gene Therapy

Prenatal gene therapy or otherwise known as intrauterine gene therapy to resolve the problems of various genetically transmitted diseases is the future of gene therapy. If successful, we can diagnose and treat certain genetic disorders before they manifest in a child. Animal studies have shown some success in the field (15).

Difficulties with Somatic Cell Gene Therapy

Multiple rounds of gene therapy are required due to its short lived nature depending upon the turn-over rate of cells replication. The rapidly dividing nature of many cells prevent the gene therapy from achieving long-term benefits. The therapeutic DNA that is introduced into the target cells must remain functional and stable for long duration. Gene therapy is particularly effective in single gene disorders, hence difficult to apply in multigenic disorders. However, Thalassemia and haemoglobinopathies, though amenable to gene therapy present technical challenges in gene regulation.

The other problem faced is with the mode and the type of vectors used for the gene delivery. Initially viral vectors were used to deliver gene but the problems of endogenous virus recombination, oncogenic effects and most importantly unexpected immune response as seen in the very first case of gene therapy remain the concerns (2).

Ongoing Research in the Field of Gene Therapy

Gene Therapy in India

In India though interest in gene therapy took some time but with financial assistance provided by different government agencies, the country has shown rapid improvement in gene therapy-related research placing India third among the major Asian countries having gene therapy laboratories (16). The main aim is to develop new institutions for gene therapy research, strengthening of existing institutions which have good expertise in this area in order to initiate work in molecular genetics for decreasing the burden of genetic disorders in the country. The pioneer of gene therapy-related research in India is Advanced Centre for Treatment, Research and Education for Cancer (ACTREC) where active work on gene therapy for head and neck cancer using synthetic vectors is being carried out (17). It is heartening to note that scientists in over dozen of labs in India are working hard with small steps in contributing towards gene therapy work as depicted in Table 1 (18-24). Hareendran et al (18) suggested that targeting specific host cellular proteins is helpful to attenuate the immune barriers which are a key obstacle in clinical application of adeno- associated virus mediated gene therapy. An alternate approach for treating Haemophilia; a using allogenic transplantation in liver where tolerance against donor antigens can be induced by in-vitro allo-antigen primed T-regulatory (Treg) cells has been studied by Kochat and her team. Shetty et al (19) have shown that naïve stemness of pluripotent cells can be generated by devising a transgenic method to express a human ortholog of protein Asrij, present on mouse embryonic stem cells (mESCs) which is essential for maintaining pluripotency. Misra et al (20) are working on selective gene transfection as a possible strategy of interest for reducing off-target gene expression and toxicity. Vij et al (21) have used nucleic acid therapeutics as an effective topical delivery system to overcome the barrier posed by different layers of the skin in cutaneous disorders. Hati Boruah et al (22) showed Ribonucleic Acid interference (RNAi) based co-transfection method could provide an alternate route of gene knockout besides providing stable cells which can be used as a cell donor for the development of transgenic cloned embryos by somatic cell nuclear transfer technique. Alternative and efficient nucleic acid transportation has been demonstrated by Kumar et al (23). Sarkar et al (24) have studied therapeutic efficacy of combining a BH3 mimetic with a novel Cancer Terminator Virus for treating advanced carcinoma prostate.

Road Ahead

Despite the above road blocks, India is fast picking up with the rest of the world in developing research related to gene therapy. Adding impetus to further research in India is the release of revised “National Ethical Guidelines for Biomedical and Health Research Involving Human Participants, 2017” and the National Guidelines for Stem Cell Research, 2017 in October, 2017 by the Indian Council of Medical Research (ICMR). These guidelines would encourage research for somatic cell gene therapy for conditions for which it is the only therapeutic option available with due permission from Department of Biotechnology (DBT) for gene constructs (25).

Gene therapy has been theoretically very sound, but its utility will be demonstrated once it comes into clinical practice. Now with the “Make in India” being a popular mantra encouraged by the Govt. of India, we should not shy out from the active involvement in gene therapy research and trials. More funding for academic research, development of dedicated departments with scope for capacity building and training, integration between researchers and clinicians, increasing public awareness and finally and most importantly with the development of Indian guidelines for gene and cell therapy clinical research trials by the ICMR will help in the transition of gene therapy from infancy to adolescence.